php encoding issue htmlentities

Question

I have user input and use htmlentities() to convert all entities. However, there seems to be some bug. When I type in

ääää öööö üüüü ääää

I

Answer 1

You must manually specify the encoding (UTF-8) for htmlentities():

echo htmlentities("ääää öööö üüüü ääää", null, "UTF-8");

Output:

ääää öööö üüüü ääää

Answer 2

it is important that 3th parameter of htmlentities matches the character set that uses the post. I supouse, you are NOT submiting utf8, as it is the default in htmlentities

in PHP

 $post = htmlentities ( $post, ENT_COMPAT, 'ISO-8859-1')  // or whatever  

in Form

 <form action="your.php" accept-charset="ISO-8859-1">

anyway, actualy I recommend you to use utf8